1. Field of the Invention
The present invention relates to a two-component reaction resin with a resin component, which contains, as curable component, at least one free radical-curable, ethylenically unsaturated compound and one agent for adjusting the reactivity and the gel time, as well as, preferably, an accelerator for the curing agent, and a hardener component, which is disposed separated therefrom to inhibit reaction and contains a curing agent for the resin of the resin component. The present invention also relates to a method of chemically fastening threaded anchor rods, reinforcing steel, threaded sleeves and screws in boreholes, using the two-component reaction resin.
2. Description of the Prior Art
Two-component reaction resins, mainly preaccelerated methacrylate resins, that is, reaction resins, which contain an accelerator for the curing agent, require the addition of stabilizers, in order to avoid undesirable, premature polymerization during storage. Usually, the stabilizers are various compounds, which are added to the free radical-curable, ethylenically unsaturated compounds of the resin component in amounts of 20 ppm to 1000 ppm. Some of the stabilizers may also be used for adjusting the gel time, that is, for a selective delay in the start of the polymerization after the resin components, containing the accelerator, is mixed with the hardener component. However, for this purpose, the amounts of stabilizers must be increased clearly, depending on the gel time aimed for, up to 5000 ppm and more. Phenolic compounds, such as hydroquinone, p-methoxyphenol, 4-t-butylpyrocatechol, 2,6-di-t-butyl-4-methylphenol or 2,4-dimethyl-6-t-butylphenol are usually used as stabilizers of this type.
These phenolic compounds, especially those, which, because of their reactivity, are particularly suitable as an inhibitor of the premature polymerization of the reaction resins addressed, have the disadvantage that they are deactivated by oxygen from the air, especially in the presence of alkaline media, such as fillers like cement, which have an alkaline action and, during the storage of a correspondingly inhibited system, lead to a slow loss of the inhibiting activity. As a consequence, the gel time is reduced to unacceptably short periods, a process, referred to as gel time drift by those of ordinary skill in the art.
In order to prevent such a gel time drift, it is proposed in the DE 195 31 649 A1, which corresponds to U.S. Pat. No. 5,854,305 that the 4-t-butylpyrocatechol, which is actually outstandingly suitable, be replaced by an inhibitor producing a stable gel time, such as piperidinyl-N-oxyl or tetrahydropyrrole-N-oxyl. However, it has turned out that these inhibitors lead to a disproportionately strong inhibition of the polymerization reaction at low temperatures and reaction resins, containing these inhibitors, are subject to strong surface inhibition by the oxygen of the air, which leads to inadequate robustness of the curing.
Sterically hindered phenols, such as 2,6-di-t-butyl-4-methylphenol and 2,4-dimethyl-6-t-butylphenol admittedly are distinctly more stable with respect to the gel time and also lead to a suitable inhibition of the polymerization at room temperature. However, at low temperatures, the quality of the cured resin and, with that, the pull-out strength of a dowel, set with the help of such an inhibited reaction resin, is unsatisfactory. Furthermore, it may be noted that most of the compounds, used as stabilizers, or not at all suitable as inhibitors.
Further attempts to solve the problem of a gel time drift, such as the treatment of the reaction resin with insoluble, organic acids, amine salts, amine accelerators, titanium complex additives and stable free radical inhibitors have also not proven to be satisfactory. Accordingly, none of these aforementioned attempts to find a solution leads to a satisfactory gel time stability of the reaction resin, especially in the presence of cement or other substances, which react alkaline, as fillers.
Accordingly, an object of the present invention is to indicate inhibitors, which produce a stable gel time for the free radical polymerization of the two-component reaction resins given above, especially on the basis of methacrylate resins, which are filled, for instance, with cement or other fillers having an alkaline reaction, and which, on the one hand, ensure the stability of the gel time during storage of such reaction resins, as can be achieved, for example, with the inhibitors known from the U.S. Pat. No. 5,854,305 and, on the other, ensure the reactivity, robustness and quality of the curing even at the low temperatures, which are achievable with the 4-t-butylpyrocatechol inhibitor.